This project is aimed at elucidating the effects of retinoic acid (RA) on the immune system. These include the effects on the humoral immune system, induction of cytotoxic T cells, natural killer cells, antibody dependent cellular cytotoxicity and lymphocyte proliferation. When appropriate, we will also investigate the specific mechanisms of RA-induced changes in functional activity. This will include obtaining information on the kinetics of RA effects and studying the activity of RA on various lymphocyte subpopulations eg. helper and suppressor cells.